Some Mac users may suddenly find that a Microsoft 365 work or school account has stopped updating in Apple Mail, Calendar or other built-in apps. The likely cause is not a bad password or a temporary server outage: Microsoft has begun phasing out Exchange Web Services in Exchange Online.
The change started on October 1, 2026, and is rolling out tenant by tenant. Organizations that still depend on EWS can temporarily keep approved apps connected, but Microsoft plans to shut the service down permanently in Exchange Online on April 1, 2027.
For individual users, the most reliable immediate workaround is to use the current Outlook for Mac app or Outlook on the web while their IT department checks the organization’s settings.
What Microsoft changed
Exchange Web Services, usually shortened to EWS, is an older interface that applications use to reach email, calendars, contacts and other Exchange data. Microsoft stopped adding major features to EWS years ago and has been directing developers toward Microsoft Graph, its newer cloud API.
Microsoft’s official EWS retirement guidance says the global disablement phase begins in October 2026. Full retirement follows in April 2027, when EWS will be permanently disabled in Exchange Online.
The rollout is not necessarily simultaneous for every company or school. A Microsoft 365 tenant may keep working while another tenant has already been switched, which explains why two Mac users with apparently similar setups can see different results.
Why Apple Mail on Mac is affected
Apple’s built-in Mail, Calendar, Contacts, Notes and Reminders apps on Mac have used EWS to synchronize Exchange Online accounts. When an organization’s EWS access is blocked, those apps may stop receiving new data even though the same account and password still work elsewhere.
MacRumors reports that Apple is working with Microsoft to move the Mac apps to Microsoft Graph in a future macOS 27 update. A release date for that transition was not confirmed in the report, so affected users should not assume a routine restart or account re-add will provide a lasting fix.
This is not a general shutdown of Microsoft email. The service continues to work through supported clients and protocols; the problem is the particular connection method used by some third-party and older applications.
Who is affected—and who is not
The change mainly matters to people who meet all of these conditions:
- They use a Microsoft 365 work or school account hosted in Exchange Online.
- They access it through an application that still relies on EWS.
- The organization has not temporarily allowed that application to continue using EWS.
Microsoft says the EWS retirement applies to Exchange Online, not an organization’s own on-premises Exchange Server. iPhone and iPad users are also not expected to lose synchronization for this reason because Apple’s mobile apps use Exchange ActiveSync rather than the Mac’s EWS path.
The current Outlook for Mac is designed to use Microsoft’s modern connection technology and should continue working. Microsoft separately advises people using legacy Outlook for Mac to switch to the current Outlook experience because the legacy client also depends on EWS.
What Mac users should do now
First, check whether the problem is limited to the Mac. Sign in to Outlook on the web and confirm that new messages and calendar events are present. If the web account works but Apple Mail does not update, contact the organization’s Microsoft 365 administrator and mention the Exchange Online EWS retirement.
Users who need immediate access can use Outlook on the web or the current Outlook for Mac. Avoid repeatedly deleting and re-adding the account unless the IT team recommends it; that may consume time without changing the organization-level EWS policy.
It is also sensible to update macOS when a compatible release arrives. However, users should review Apple’s release notes or their employer’s deployment guidance rather than assuming every macOS 27 update includes the Microsoft Graph migration.
What Microsoft 365 administrators can do
Administrators should review EWS usage reports and identify every application, backup tool and business workflow that still calls Exchange Online through EWS. Apple’s Mac apps may be the most visible symptom, but they may not be the only dependency.
Microsoft provides an EWSEnabled organization setting and an EWSAllowedAppIDs allow list for temporary, controlled access during the transition. The Exchange Team’s guidance explains that approved application IDs can be permitted while other EWS traffic remains blocked.
That is a bridge, not a permanent solution. Administrators should migrate internal software to Microsoft Graph, update third-party products, and test replacement clients before April 1, 2027. Microsoft says no EWS access will remain in Exchange Online after final retirement.
Why Microsoft is retiring EWS
Microsoft says the older service no longer meets its requirements for security, scalability and reliability. The company also notes that an EWS dependency was involved in the 2024 Midnight Blizzard security incident, increasing the urgency of the migration.
Moving to Microsoft Graph gives developers a newer authentication and permissions model, but the transition can expose applications that organizations forgot were still using EWS. The phased shutdown is therefore both a product change and a deadline for IT teams to finish their dependency audits.
The practical bottom line
If Microsoft 365 mail suddenly disappears from Apple Mail on a Mac, do not assume the mailbox itself is gone. Check Outlook on the web, switch temporarily to the current Outlook app if necessary, and ask the organization’s administrator whether EWS was disabled.
The temporary allow-list option can restore service for approved apps during the migration period, but it only buys time. April 1, 2027 is the hard cutoff for EWS in Exchange Online, so Apple, Microsoft, software vendors and IT departments all need a modern replacement in place before then.
Featured image: Luke Southern via Unsplash.